Recently, mobility support in the IP layer such as MobileIPv6 (Mobility Support in IPv6, RFC3775) is actively researched and developed. The MobileIP is a third-layer protocol in the OSI (Open System Interconnection) seven-layer model and is a technology of hiding client movement (such as switching of networks/communication media and momentary disconnection of communication) from a higher-order application to continue communication. The MobileIP is configured by nodes called a mobile node (MN) *home agent (HA) and a correspondent node (CN).
The mobile node (MN) has an always invariable address called a home address, and a node managing that address is the home agent (HA) When the MN is connected to a network other than a home link that is a link of the HA, the MN acquires an address called a care-of address (CoA) using some means (such as RA and DHCPv6). The acquired CoA is supplied to the HA by a message called the Binding Update.
As a result, if a node (=CN) that wants to communicate with the MN transmits a packet to the home address, the packet once arrives at HA since the home address is an address of a link managed by the HA. The HA then transfers the packet to the CoA which the home address is related to. As a result, the MN can always communicate by means of the home address. At the MN, an application running on the MN always use an IP address called the home address to communicate.
The CoA is used for a source address or destination address of an actual IPv6 (Internet Protocol Version 6) packet. An application is notified of the home address using a technology such as the IPv6 on IPv6 encapsulation and the mobility header to hide the IPv6 address (CoA) actually used. As a result, the application has the following characteristics.
(1) If a connection to a network is kept, communication can always be performed by means of the home address. (2) Handover to different networks can be performed during communication. That is, a MobileIP support terminal can have a plurality of communication media (e.g., NIC: Network Interface Card) and the handover can be performed across a plurality of communication media. A known problem of the MobileIP is which communication medium is used, i.e., which address is used for the CoA when a MobileIP support terminal has a plurality of communication media.
If a plurality of CoAs is included, it is often said that the MobileIP can realize the multi-home that concurrently uses a plurality of communication media. However, the multi-home cannot be realized with the actual MobileIP specification. Therefore, because of a concept that a communication counterpart should be notified of all the CoAs, the “draft-wakikawa-mobileip-multiplecoa” is proposed as a means of realizing the multi-home, which is a specification of the MobileIP when a plurality of CoAs is included. Patent document 1 is known as a technology of using a plurality of media at the same time.
Patent Document 1: Published Japanese translation (Publication No. 2004-528764) of PCT publication (WO2002/080452)